U.S. patent application number 10/946033 was filed with the patent office on 2005-06-09 for low-loss reconfigurable reflector array antenna.
This patent application is currently assigned to ALCATEL. Invention is credited to Legay, Herve, Salome, Beatrice.
Application Number | 20050122273 10/946033 |
Document ID | / |
Family ID | 34178941 |
Filed Date | 2005-06-09 |
United States Patent
Application |
20050122273 |
Kind Code |
A1 |
Legay, Herve ; et
al. |
June 9, 2005 |
Low-loss reconfigurable reflector array antenna
Abstract
A reflector array antenna is divided into independent subarrays
each comprising at least two radiating elements adapted firstly to
collect signals delivered by a source and having at least one
chosen first polarization and secondly to send phase-shifted
signals having at least one chosen second polarization orthogonal
to the first polarization. Each subarray sums the collected signals
as a function of a chosen first phase law so that they correspond
to a chosen source pointing direction, applies a chosen phase shift
to the summed signals, and distributes the phase-shifted signals
between the radiating elements as a function of a chosen second
phase law so that the radiating elements of each subarray radiate
them in a pointing direction of a chosen area. The combining and
distribution are effected separately and the subarrays are
therefore of a nonreciprocal type.
Inventors: |
Legay, Herve; (Plaisance Du
Touch, FR) ; Salome, Beatrice; (Lanta, FR) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
ALCATEL
|
Family ID: |
34178941 |
Appl. No.: |
10/946033 |
Filed: |
September 22, 2004 |
Current U.S.
Class: |
343/754 ;
342/370; 343/700MS |
Current CPC
Class: |
H01Q 3/46 20130101 |
Class at
Publication: |
343/754 ;
343/700.0MS; 342/370 |
International
Class: |
H01Q 003/22; H01Q
019/06 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 23, 2003 |
FR |
03 11 109 |
Claims
There is claimed:
1. A reflector array antenna divided into independent subarrays
each comprising: at least two radiating elements adapted firstly to
collect signals delivered by a source and having at least one
chosen first polarization and secondly to send phase-shifted
signals having at least one chosen second polarization orthogonal
to the first polarization, combination means adapted to sum said
collected signals as a function of a chosen first phase law so that
they correspond to a chosen source pointing direction, phase
control means adapted to apply a chosen phase shift to the summed
signals, and distribution means adapted to distribute said
phase-shifted signals between said radiating elements as a function
of a chosen second phase law so that said radiating elements of
each subarray radiate them in a pointing direction of a chosen
area, in which antenna said combination means and said distribution
means are separate so that said subarrays are of a nonreciprocal
type.
2. The antenna claimed in claim 1, wherein said phase control means
and said distribution means of the antenna are configurable so that
said pointing direction of the chosen area is variable.
3. The antenna claimed in claim 1, wherein said phase control means
are phase shifters.
4. The antenna claimed in claim 3, wherein said phase shifters
comprise at least two delay lines with different configurations and
at least one microelectromechanical system.
5. The antenna claimed in claim 1, wherein said combination means
comprise a transmission line having branches coupled to said
radiating elements to collect in parallel the signals having said
first polarization and conformed to define said first phase
law.
6. The antenna claimed in claim 1, wherein said combination means
comprise a transmission line comprising line portions connecting
said radiating elements to each other to collect in series the
signals having said first polarization and conformed to define said
first phase law.
7. The antenna claimed in claim 1, wherein said distribution means
comprise a transmission line having branches coupled to said
radiating elements to distribute in parallel the phase-shifted
signals and conformed to define said second phase law.
8. The antenna claimed in claim 1, wherein said distribution means
comprise a transmission line consisting of line portions connecting
said radiating elements to each other to distribute in series the
phase-shifted signals and conformed to define said second phase
law.
9. The antenna claimed in claim 1, wherein each subarray is
planar.
10. The antenna claimed in claim 1, wherein each subarray is
linear, its radiating elements being aligned in a chosen
direction.
11. The antenna claimed in claim 9, wherein said subarrays are
installed in parallel to constitute a strip of at least two
subarrays.
12. The antenna claimed in claim 11, comprising at least two
parallel strips.
13. The antenna claimed in claim 1, wherein said radiating elements
are adapted to collect signals having said chosen first and second
polarizations and comprising first polarization selection means
interleaved between said radiating elements and said combination
means and second polarization selection means interleaved between
said distribution means and second said radiating elements, said
first and second polarization selection means being adapted to
select one of said first and second polarizations on command so
that said antenna is able to operate in two different polarization
modes.
14. The antenna claimed in claim 1, wherein said radiating elements
are adapted to collect signals having said chosen first and second
polarizations and comprise polarization selection means adapted to
select one of said first and second polarizations on command so
that said antenna is able to operate in two different polarization
modes.
15. The antenna claimed in claim 5, wherein each transmission line
is implemented in a technology chosen from a group comprising a
microstrip technology, a coplanar technology and a triplate
technology.
16. The antenna claimed in claim 1, wherein said radiating elements
are chosen from a group comprising multilayer structures with
radiating patches, microstrip resonators, slots and dielectric
resonators.
17. The antenna claimed in claim 1, wherein said radiating elements
are coupled to said combination means and to said distribution
means by direct contact.
18. The antenna claimed in claim 1, wherein said radiating elements
are coupled electromagnetically to said combination means and to
said distribution means.
19. The antenna claimed in claim 1, wherein each subarray comprises
amplifier means adapted to amplify said summed waves before they
are sent and/or once they have been collected.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] filed Sep. 23, 2003, the disclosure of which is hereby
incorporated by reference thereto in its entirety, and the priority
of which is hereby claimed under 35 U.S.C. .sctn.119.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The field of the invention is that of array antennas and
more particularly that of reflector array antennas.
[0004] 2. Description of the Prior Art
[0005] There are two large families of array antennas, namely
phased array antennas (PAA) and reflector array antennas (RAA).
[0006] Array antennas must be reconfigurable in order to move from
one coverage area ("spot") to another.
[0007] In the case of phased array antennas, reconfigurability may
be obtained by dividing the array into subarrays each associated
with an active phase control device. The reconfigurability of the
antenna then depends on only one constraint, namely the dimensions
of each subarray, which depend on the dimensions of the coverage
area to which the antenna must point.
[0008] In the case of reflector array antennas, it is essential
that the radiating elements intercept with minimum losses the waves
carrying the transmitted signals, which are delivered by a source.
Now, the angle of incidence at which the radiating elements receive
the waves varies as a function of their positions relative to the
source. For certain arrays it may vary from 0.degree. to
50.degree.. An angular variation of this magnitude makes it
particularly difficult both to receive waves coming from the source
with a high gain and to transmit (or send) received waves over the
whole of the pointed to coverage area with a high gain.
[0009] Reflector array antennas therefore routinely employ
relatively undirectional radiating elements, with a typical
dimension from 0.6.lambda. to 0.7.lambda., where .lambda.
represents the operating wavelength. Reconfiguring the antenna
diagram of this kind of antenna therefore necessitates equipping
each radiating element with a phase control device. However, this
kind of solution may lead to prohibitive costs.
[0010] Thus an object of the invention is to improve on this
situation in the case of reflector array antennas.
SUMMARY OF THE INVENTION
[0011] To this end it proposes a reflector array antenna divided
into independent subarrays each comprising:
[0012] at least two radiating elements adapted firstly to collect
signals delivered by a source and having at least one chosen first
polarization and secondly to send phase-shifted signals having at
least one chosen second polarization orthogonal to the first
polarization,
[0013] combination means adapted to sum the collected signals as a
function of a chosen first phase law so that they correspond to a
chosen source pointing direction,
[0014] phase control means adapted to apply a chosen phase shift to
the summed signals, and
[0015] distribution means adapted to distribute the phase-shifted
signals between the radiating elements as a function of a chosen
second phase law so that the radiating elements of each subarray
radiate them in a pointing direction of a chosen area,
[0016] in which antenna the combination means and the distribution
means are separate so that the subarrays are of a nonreciprocal
type.
[0017] According to another feature of the invention, the phase
control means and the distribution means of the antenna are
configurable so that the pointing direction of the chosen area is
variable.
[0018] Each subarray may have other features, and in particular,
either separately or in combination:
[0019] the phase control means may be phase shifters that comprise
at least two delay lines with different configurations and at least
one switch, for example a microelectromechanical system,
[0020] the combination means may comprise a transmission line
having branches coupled to the radiating elements to collect in
parallel the signals having the first polarization and conformed to
define the first phase law,
[0021] the combination means may comprise a transmission line
comprising line portions connecting the radiating elements to each
other to collect in series the signals having the first
polarization and conformed to define the first phase law,
[0022] the distribution means may comprise a transmission line
having branches coupled to the radiating elements to distribute in
parallel the phase-shifted signals and conformed to define the
second phase law,
[0023] the distribution means may comprise a transmission line
consisting of line portions connecting the radiating elements to
each other to distribute in series the phase-shifted signals and
conformed to define the second phase law,
[0024] each subarray may be planar,
[0025] each subarray may be linear, its radiating elements being
aligned in a chosen direction,
[0026] the subarrays may be installed in parallel to constitute a
strip of at least two subarrays,
[0027] the antenna may comprise at least two parallel strips,
[0028] the radiating elements may be adapted to collect signals
having the chosen first and second polarizations and comprising
first polarization selection means interleaved between the
radiating elements and the combination means and second
polarization selection means interleaved between the distribution
means and second the radiating elements, the first and second
polarization selection means being adapted to select one of the
first and second polarizations on command so that the antenna is
able to operate in two different polarization modes,
[0029] the radiating elements may be adapted to collect signals
having the chosen first and second polarizations and comprise
polarization selection means adapted to select one of the first and
second polarizations on command so that the antenna is able to
operate in two different polarization modes,
[0030] each transmission line may be implemented in a technology
chosen from a group comprising a microstrip technology, a coplanar
technology and a triplate technology,
[0031] the radiating elements may be chosen from a group comprising
multilayer structures with radiating patches, microstrip
resonators, slots and dielectric resonators,
[0032] the radiating elements may be coupled to the combination
means and to the distribution means by direct contact,
[0033] the radiating elements may be coupled electromagnetically to
the combination means and to the distribution means, and
[0034] each subarray may comprise amplifier means adapted to
amplify the summed waves before they are sent and/or once they have
been collected.
[0035] Other features and advantages of the invention will become
apparent on reading the following detailed description and
examining the appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] FIG. 1 is a block diagram of a subarray of a reflector array
antenna according to the invention.
[0037] FIG. 2 is a diagrammatic representation of one embodiment of
a nonreciprocal planar subarray.
[0038] FIG. 3 is a view in cross section of a reflector array
antenna according to the invention comprising two nonreciprocal
planar subarrays.
[0039] FIG. 4 is a diagrammatic representation of a first
embodiment of a nonreciprocal linear subarray.
[0040] FIG. 5 is a diagrammatic representation of a second
embodiment of a nonreciprocal linear subarray.
[0041] FIGS. 6A and 6B are diagrammatic representations of two
portions of a third embodiment of a nonreciprocal linear
subarray.
[0042] FIG. 7 is a diagrammatic representation of a fourth
embodiment of a nonreciprocal linear subarray.
[0043] FIG. 8 is a diagrammatic representation of a fifth
embodiment of a nonreciprocal linear subarray adapted for dual
polarization.
[0044] FIG. 9 is a diagrammatic representation of a sixth
embodiment of a nonreciprocal linear subarray adapted for dual
polarization.
[0045] FIG. 10 is a diagrammatic representation of a seventh
embodiment of a nonreciprocal linear subarray adapted for dual
polarization.
[0046] FIG. 11 is a diagrammatic representation of one example of a
strip of nonreciprocal linear subarrays.
[0047] FIG. 12 is a diagrammatic representation of one example of
combined nonreciprocal planar subarray strips.
[0048] FIG. 13 is a diagrammatic representation of one embodiment
of a radiating element comprising asymmetrical slots.
[0049] FIG. 14 is a diagrammatic representation of one embodiment
of a radiating element comprising symmetrical slots.
[0050] FIG. 15 is a variant of FIG. 7 showing signal amplification
means.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0051] The appended drawings constitute part of the description of
the invention and may, if necessary, contribute to the definition
of the invention.
[0052] The invention is explained first with reference to FIG.
1.
[0053] A reflector array antenna A comprises first of all a source
S delivering waves comprising signals to be transmitted into a
chosen solid angle whose main direction is known as the source
pointing direction (DPS). The antenna A also comprises a plurality
of subarrays SR with a high gain for receiving waves delivered by
the source S and transmitting them in a chosen solid angle whose
main direction is known as the antenna pointing direction (DPA), in
order to cover a chosen area with a high gain.
[0054] According to the invention, each of the subarrays SR, which
are independent of each other, comprises, first of all, at least
two radiating elements ERi (here i=1 to 4, but may take any other
value greater than or equal to 2), firstly for collecting the
signals delivered by the source S that reach them in the form of
waves that have at least one chosen first polarization P1, and
secondly for sending phase-shifted signals having at least one
chosen second polarization P2 orthogonal to the first polarization.
Each radiating element ERi delivers the signals that it has
collected to an output 0 to which it is coupled.
[0055] Each subarray SR also comprises combination means fed with
signals collected via the various outputs O and summing them as a
function of a chosen first phase law in order for them to
correspond to the chosen source pointing direction DPS.
[0056] Each subarray SR further comprises phase control means MCP
fed with signals summed by the combination means MC and applying a
chosen phase-shift to them.
[0057] Finally, each subarray SR comprises distribution means MD
fed by the phase control means MCP with summed and phase-shifted
signals and distributing them between the radiating elements ERi,
via inputs I, as a function of a chosen second phase law so that
the radiating elements radiate them in the antenna pointing
direction DPA with the second polarization P2.
[0058] The subarrays SR are preferably of the nonreciprocal type.
In a nonreciprocal subarray SR, the combination means MC and the
distribution means MD are separate. They therefore constitute two
separate feeder circuits.
[0059] Because of the two separate feeder circuits, it is possible
to handle reception and transmission separately, and consequently
to obtain a high gain for reception and a high gain for
transmission (sending), provided that the pitch of the array is
sufficiently small (typically 0.6.lambda. to 0.7.lambda.). The
dimensions of the subarray SR are then chosen as a function of the
maximum scanning angle necessary for transmission in the antenna
pointing direction DPA, in the manner of an active phased array
antenna.
[0060] A nonreciprocal subarray SR may be of planar or linear
form.
[0061] Here the term "planar subarray" means a subarray SR of the
type shown in FIG. 2. In this kind of subarray SR, the radiating
elements ERi (here i=1 to 4) are disposed in a plane, for example
at the four corners of a rectangular parallelepiped. In the example
shown, each radiating element ERi delivers at its output 0 signals
having a vertical first polarization P1 and is adapted to send
summed signals having a horizontal second polarization P2.
[0062] Each output 0 constitutes the end of a branch R1 of a first
transmission line LT1 connected to the input of the phase control
means MCP and constituting the combination means MC. The
configurations of the transmission line LT1 and its branches R1 are
chosen to compensate the differences between the paths taken by the
waves between the source S and the various radiating elements ERi
in accordance with the first phase law associated with the source
pointing direction DPS for the subarray SR concerned. This
compensation constitutes what is referred to hereinabove as
combining the signals.
[0063] Here, all the radiating elements ERi feed the combination
means MC in parallel. However, a serial feed variant may be
envisaged. In this case, the transmission line LT1 consists of
portions of lines that connect the radiating elements ERi to each
other.
[0064] Moreover, each input I constitutes the end of a branch R2 of
a second transmission line LT2 connected to the output of the phase
control means MCP and constituting the distribution means MD. The
phase shift applied by the phase control means MCP and the
configurations of the transmission line LT2 and its branches R2 are
chosen in accordance with the second phase law associated with the
antenna pointing direction DPA.
[0065] Here, distribution means MD feed the radiating elements ERi
in parallel. However, a serial feed variant may be envisaged. In
this case, the transmission line LT2 consists of portions of lines
that connect the radiating elements ERi to each other.
[0066] It is important to note that, within an antenna A, the first
phase law applied by the combination means MC may vary from one
subarray to another because of their respective positions relative
to the source S.
[0067] The transmission lines LT1 and LT2 and their branches R1 and
R2 are preferably implemented in the microstrip technology.
However, the transmission lines LT1 and LT2 and their branches R1
and R2 may instead be implemented in the triplate or coplanar
technology.
[0068] Moreover, as seen most clearly in FIG. 3, because of the
crossing over of the transmission lines LT1 and LT2, the
combination means MC (LT1 and R1) and the distribution means MD
(LT2 and R2) are preferably implemented at different levels of the
structure of the subarray SR. In this example, the transmission
lines are coupled directly (by contact) to the radiating elements
ERi. However, a variant may be envisaged in which the coupling is
effected by means of slots. In this case, the combination means MC
and the distribution means MD may be installed at two different
levels of the rear face.
[0069] Embodiments of nonreciprocal linear subarrays according to
the invention are described next.
[0070] Here, the expression "linear subarray" means a subarray SR
of the type shown in FIG. 4 or one of the variants thereof shown in
FIGS. 5 to 10 and 15.
[0071] In a nonreciprocal subarray SR, the radiating elements ERi
are disposed one after the other in a chosen direction OX. This
disposition is particularly well suited, although not exclusively
so, to synthetic aperture radar (SAR) antennas. Moreover, the
combination means MC and the distribution means MD do not cross
over, in contrast to planar subnetworks in which the combination
means MC and the distribution means MD cross over because they are
formed at two different levels.
[0072] In the FIG. 4 embodiment, each radiating element ERi (here
i=1 to 4) delivers (at its output O) signals having the horizontal
first polarization P1 and is adapted to send summed signals having
a vertical second polarization P2. The radiating elements ERi of
the subarray SR feed the combination means MC with signals of
polarization P1 in parallel and the combination means combine them
in accordance with the first phase law to feed the input of the
phase control means MCP. The phase control means MCP feed summed
and phase-shifted signals to the distribution means MD which are at
the same level as the combination means MC and the distribution
means MD, for example. Finally, the distribution means MD
distribute the summed and phase-shifted signals to the radiating
elements ERi in parallel and in accordance with the second phase
law.
[0073] Because of the lack of space, the phase control means MCP
are installed at a different level from the combination means MC
and the distribution means MD. For this reason they are shown in
dashed line.
[0074] In this embodiment, each output O of a radiating element ERi
constitutes the end of a branch R1 of a first transmission line LT1
connected to the input of the phase control means MCP by a first
transition TR1 and constituting the combination means MC. The
configurations of the transmission line LT1 and its branches R1 are
chosen to compensate the differences between the paths taken by the
waves between the source S and the various radiating elements ERi
in accordance with the first phase law associated with the source
pointing direction DPS.
[0075] Each input I constitutes the end of a branch R2 of a second
transmission line LT2 connected to the output of the phase control
means MCP by a second transition TR2 and constituting the
distribution means MD. To be more precise, the second transition
TR2 is here connected to the output of the phase control means MCP
by an auxiliary transmission line LT3.
[0076] The configurations of the auxiliary transmission line LT3
and the transmission line LT2 and its branches R2 are chosen in
accordance with the second phase law associated with the antenna
pointing direction DPA.
[0077] The transmission lines LT1 and LT2 and their branches R1 and
R2 are also preferably implemented in the microstrip technology and
on the same layer as the lower radiating patches of the radiating
elements ERi. However, the transmission lines LT1 and LT2 and their
branches R1 and R2 may instead be implemented in the triplate or
coplanar technology.
[0078] Here, the patches of the radiating elements ERi are
circular, but they could be square.
[0079] If it is possible to install the phase control means MCP at
the same level as the combination means MC and the distribution
means MD, the configuration shown in FIG. 5 may be used, for
example.
[0080] This variant uses all the components of the FIG. 4 subarray
but differs from the latter in that, firstly, the outputs O of the
radiating elements ER1 and ER2 face each other, like those of the
radiating elements ER3 and ER4, and, secondly, the phase control
means MCP are at the same level as the combination means MC and the
distribution means MD.
[0081] Because of this configuration, the signals delivered by the
radiating elements ER1 and ER2 (respectively ER3 and ER4) at their
respective outputs o have antiparallel polarizations here. A phase
shifter D is therefore provided on the branch R1 that connects the
radiating element ER1 (respectively ER3) to the transmission line
LT1 for applying a phase shift of 180.degree. to the signals that
it receives before they are combined with the signals coming from
the radiating element ER2 (respectively ER4).
[0082] The embodiment shown in FIGS. 6A and 6B provides a better
indication of the separation of the phase control means MCP, on the
one hand, and the combination means MC and the distribution means
MD, on the other hand, referred to above with reference to FIG.
4.
[0083] In this embodiment, the distribution means MD feed the
radiating elements ERi in parallel with summed and phase-shifted
signals to be sent with a vertical linear second polarization P2.
It may be noted that here the inputs I of the radiating elements
ERi and ER2 are placed "at the bottom" of the lower patches PI
(with respect to the vertical direction of the page), whereas the
inputs I of the radiating elements ER3 and ER4 are placed "at the
top" of the lower patches PI (also with respect to the vertical
direction of the page). Consequently, the polarization of the
signals emitted by the radiating elements ER3 and ER4 is
antiparallel to that of the signals emitted by the radiating
elements ER1 and ER2. This therefore requires that the signals
coming either from ER1 and ER2 or from ER3 and ER4 be phase shifted
180.degree., as shown in FIG. 5.
[0084] As shown in FIG. 6A, each radiating element ERi here
consists in particular of a lower radiating patch PI that is on the
layer comprising the combination means MC and the distribution
means MD and an upper radiating patch PS (shown in dashed outline)
that is above a dielectric layer in turn above the layer comprising
the lower patches PI, the combination means MC, and the
distribution means MD.
[0085] The phase control means MCP are implemented in a layer of
the structure that is preferably to the rear of the ground plane
(not shown) and the layer comprising the combination means MC and
the distribution means MD (see FIG. 6B). Also, the multilayer
structure is surrounded by metal walls PM.
[0086] In this embodiment, each output O of a radiating element ERi
constitutes the end of a branch R1 of a first transmission line LT1
connected to the input of the phase control means MCP by a first
transition TRI and constituting the combination means MC. The
configurations of the transmission line LT1 and its branches R1 are
chosen to compensate the differences between the paths taken by the
waves between the source S and the various radiating elements ERi
in accordance with the first phase law associated with the source
pointing direction DPS.
[0087] Here, all the radiating elements ERi feed the combination
means MC in parallel with signals having a horizontal first
polarization P1.
[0088] Each input I constitutes the end of a branch R2 of a second
transmission line LT2 connected to the output of the phase control
means MCP by a second transition TR2 and constituting the
distribution means MD. To be more precise, here the second
transition TR2 is connected to the output of the phase control
means MCP by an auxiliary transmission line LT3.
[0089] The configurations of the auxiliary transmission line LT3
and the transmission line LT2 and its branches R2 are chosen in
accordance with the second phase law associated with the antenna
pointing direction DPA.
[0090] The transmission lines LT1 and LT2 and their branches R1 and
R2 are also preferably implemented in the microstrip technology and
on the same layer as the lower patches PI. However, the
transmission lines LT1 and LT2 and their branches R1 and R2 may
instead be implemented in the triplate or coplanar technology.
[0091] In one embodiment, the combination means MC and the
distribution means MD may be placed to the rear of the ground
plane. In this case, each radiating element ERi is fed by two
virtual transitions connected to its excitation points. This
embodiment requires room to be freed up at the center for
installing the phase control means MCP, which imposes an excitation
configuration similar to that of FIG. 5 and thus the use of
180.degree. phase shifters MM.
[0092] Another embodiment of a linear nonreciprocal subarray
according to the invention is described next with reference to FIG.
7. This variant comprises most of the components of the FIG. 4
subarray, but differs from the latter in that, for reception, the
radiating elements ERi are coupled to each other in series.
[0093] To be more precise, in this embodiment, the output O of the
first radiating element ER1 feeds a first portion P1 of the
transmission line LT1 connected to the second radiating element
ER2, whose output feeds a second portion P2 of the transmission
line LT1 connected to the third radiating element ER3, whose output
feeds a third portion of the transmission line LT1, and here the
output of the fourth radiating element ER4 feeds a fourth portion
P4 of the transmission line LT1, arranged differently from the
other portions P1 to P3 in order to compensate the antiparallel
excitation of the fourth radiating element ER4. The transmission
line LT1 feeds the phase control means MCP, which feed the
transmission line LT2 whose branches are connected to the inputs I
of the radiating elements ERi.
[0094] This embodiment is particularly beneficial if it includes
"reversible" phase control means MCP, as this enables the antenna A
to operate in two polarization modes because, instead of feeding
the transmission line LT1 serially with signals of horizontal
polarization P1, the radiating elements ERi may feed the
transmission line LT2 in parallel with summed and phase shifted
signals to be sent with a vertical second polarization P2. In this
case, the transmission line LT1 feeds the radiating elements ERi
serially with signals of horizontal polarization P1.
[0095] FIGS. 8 and 9 show two variants of this embodiment. They
enable the antenna A to operate in two different polarization
modes.
[0096] The first variant of the subarray SR, shown in FIG. 8,
differs from the FIG. 7 subarray in that it uses switching modules
MCT on the branches of the transmission line LT1 and on the
transmission line LT2. To be more precise, in the configuration
shown, the switching modules MCT (which are duplicated everywhere
to allow operation in both directions) have a first setting for
applying the phase law associated with the antenna pointing
direction DPA. Signals having a vertical first polarization P1 are
then collected in parallel, and summed and phase-shifted signals to
be sent with a horizontal second polarization P2 are distributed
serially. On the other hand, when all the switching modules MCT are
in a second setting, the phase law associated with the source
pointing direction DPS may be applied. This adapts the polarization
to that of the source S. Signals having a horizontal first
polarization are then collected serially, and summed and
phase-shifted signals to be sent with a vertical second
polarization are distributed in parallel.
[0097] As may be seen in FIG. 8, the two channels that connect the
inputs (or outputs) of the switching modules MCT to the branches R1
or to the transmission line LT2 do not have the same configuration
because they are associated with different phase laws.
[0098] The second variant of the subarray SR, shown in FIG. 9,
differs from the FIG. 7 subarray in that the patches of the
radiating elements ERi are no longer fed from their sides, but from
their corners, so as to excite both polarizations simultaneously,
and in that switching modules MCT are used in the radiating
elements ERi to select one of the two excited polarizations, both
for collection and for sending.
[0099] It is important to note that the dual polarization is not
necessarily linear. It may be circular. In this case, as shown in
FIG. 10, the radiating elements ERi may be microstrip resonators
truncated along their diagonal or slightly rectangular microstrip
resonators, for example. In the FIG. 10 variant, the switches MCT
enabling operation with dual polarization are not shown. However,
in reality, they are placed at the input and at the output of the
radiating elements ERi, as in the FIG. 8 embodiment.
[0100] Although this has not been mentioned as yet, making up
strips of subarrays SR in a chosen direction enables the antenna
pointing direction DPA to be varied, in other words renders the
antenna reconfigurable.
[0101] A strip B of this kind, in the case of linear subarrays SR,
is shown diagrammatically in FIG. 11. In this case, as shown in the
figure, the subarrays SR of a strip B are placed one against the
other parallel to their extension direction (here the direction
OX). The antenna A is then reconfigurable in the direction OY (in
elevation), i.e. in the plane perpendicular to the direction
OX.
[0102] Also, as shown in FIG. 12, the antenna A may comprise a
plurality of parallel strips B of planar subarrays in order for it
to be reconfigurable both in the direction OY (in elevation), i.e.
in the plane perpendicular to the direction OX, and in the
direction OX, i.e. in the plane perpendicular to the direction
OY.
[0103] As mentioned hereinabove, the radiating elements ERi
preferably take the form of a conventional multilayer structure
comprising, in particular, a lower radiating conductive patch PI
coupled, firstly, to the input I and/or to the output 0, and,
secondly, to an upper radiating conductive patch PS for collecting
waves coming from the source S and sending the collected waves
after they have been converted. The coupling between the upper
radiating patches PS and the lower radiating patches PI of a
radiating element ERi may be effected either directly by
conduction, by means of a conductive layer or vias, or
electromagnetically, by means of a layer of dielectric
material.
[0104] It is important to note that if the subarray SR is to be
able to operate with two polarizations (dual mode), its radiating
elements ERi must be adapted accordingly. For example, two
asymmetrical slots FA1 and FA2, as shown in FIG. 13, or two
symmetrical slots FS1 and FS2, as shown in FIG. 14, may be
integrated into the multilayer structure of the radiating elements
ERi. These slots may be formed in the ground plane of the
structure. The combination means MC are then installed on the rear
face of the ground plane and coupled to the radiating patches via
the slots.
[0105] Further information on the structure of the radiating
elements and the slots may be found in the following documents in
particular:
[0106] "Dual-polarized wideband microstrip antenna", S. C. GAO et
al, Electronics Letters, 30 Aug. 2001, Vol. 37, N.sup.o 18,
[0107] "Aperture coupled patch antennas with wide-bandwidth and
dual polarization capabilities", C. M. TAO et al, Antennas and
Propagation Society International Symposium, 1988, AP-S, Digest,
June 1988, Vol. 3, pages 936-939,
[0108] "Dual-polarized array for signal-processing applications in
wireless communications", B. LINDMARK et al, IEEE Transactions on
Antennas and Propagation, Vol. 46, Issue: 6 Jun. 1998, pages
758-763,
[0109] "Wideband dual-polarized microstrip patch antenna", S. C.
GAO et al, Electronics Letters, 27 Sep. 2001, Vol.37, N.sup.o
20,
[0110] "Investigations into a power-combining structure using a
reflect array of dual feed aperture-coupled microstrip patch
antennas", Marek E. Bialkowsksi, IEEE Transactions on Antennas and
Propagation, Vol. 50, Issue: 6 June 2002, pages 841-849.
[0111] The use of symmetrical slots FS is preferred because it
achieves better isolation between the two polarizations and does
not generate high levels of crossed polarization.
[0112] For example, in the case of an SAR type application in the X
band at 9.8 GHz, the substrate S, which carries the feeder circuits
and the lower radiating patches PI, may be made from a PTFE type
material having a dielectric constant of approximately 3.2, a loss
tangent of approximately 0.003 at 10 GHz, a thickness of
approximately 0.79 mm, and a copper thickness of approximately 17
.mu.m. The separators placed between the radiating patches and the
slots FA or FS may be made from a Rohacell 31 type material, for
example, having a dielectric constant of approximately 1.05, a loss
tangent of approximately 0.0002 at 2.5 GHz, and a thickness of
approximately 2 mm. In this case, the pitch of the array (i.e. the
distance between the radiating elements ERi) is made substantially
equal to 20 mm, which corresponds to 0.65.lambda. when the
frequency is equal to 9.8 GHz.
[0113] The phase control means MCP of each subarray SRi preferably
take the form of phase shifters and more preferably the form of
delay lines with different configurations (so as to apply different
phase shifts), coupled to at least one microelectromechanical (MEM)
system providing the switching function. These systems are
particularly advantageous because they have very low insertion
losses, typically of the order of 0.1 dB for frequencies as high as
40 GHz.
[0114] The state of the MEM system is controlled by applying
electrical voltages.
[0115] As shown in FIG. 15, each subarray SR may further comprise
low-noise amplifier (LNA) means and/or high-power amplifier (HPA)
means for providing quasi-optical amplification of the summed waves
before or after phase shifting by the phase control means MCP.
[0116] In the embodiment shown, the subarray SR comprises a
circulator CR connected firstly to the transmission line LT2 and
secondly to the amplifier means LNA and HPA, which are also
connected to a switch MCT, which is itself connected to the phase
control means MCP.
[0117] Thus, according to the states of the circulator CR and the
switch MCT, the signals arrive either at the LNA to be amplified
therein before "ascending" to the phase control means MCP and then
the radiating elements ERi (enabling operation of the antenna in
receive mode), or to the HPA to be amplified therein before
"descending" to the radiating elements ERi (enabling operation of
the antenna in transmit mode).
[0118] The amplifier means LNA and HPA may take the form of
amplifier microchips, for example MMICs.
[0119] The invention is not limited to the embodiments of antennas
described hereinabove by way of example only, but encompasses all
variants that the person skilled in the art might envisage that
fall within the scope of the following claims.
[0120] Accordingly, the number of radiating elements in each
subarray may be any number at least equal to two.
[0121] The number of subarrays of an antenna may be any number at
least equal to two.
[0122] Embodiments of subarrays have been described in which the
radiating elements consisted of a multilayer structure comprising
radiating patches. The invention is not limited to this type of
radiating element alone, however. It relates equally to subarrays
equipped with radiating elements such as microstrip resonators,
slots, or dielectric resonators.
* * * * *